Iain Martin is a political commentator, and a former editor of The Scotsman and former deputy editor of The Sunday Telegraph. He is the author of Making It Happen: Fred Goodwin, RBS and the men who blew up the British economy, published by Simon & Schuster.. As well as this blog, he writes a column for The Sunday Telegraph. You can read more about Iain by visiting his website

Two years ago I formed the Don't Underestimate Ed Miliband Association (DUEMA), believing that the Labour leader's internal and external opponents were foolish to write him off. On Twitter today there was much Opposition criticism of Cameron's speech. But the wiser heads in Labour should forget about sniping and start thinking instead about forming their own pressure group: DUDCA (the Don't Underestimate David Cameron Association).

Cameron got himself back in business here in Birmingham. I don't mean that he's suddenly on track to win the next general election or that the electoral landscape has been transformed. It hasn't. The essential facts remain the same. Labour starts not from below 30 per cent of the vote, which it polled in 2010 with Gordon Brown, but easily up in the mid-30s. Those anti-Blair and anti-Iraq war voters have gone home to Labour, making it even more difficult for the Conservatives next time around. Then there is the rise of Ukip, draining the Tory party of activists, money and a section of its support.

Up against all that, a speech – albeit a brilliant speech – is still just a speech. The Government continues to make some appalling mistakes on the tax system, Europe and the economy.

But his speech will change the atmospherics in important respects. The Tory tribe arrived here in a bad mood after a terrible year for the government. They leave rather buoyed up. The conference was not exciting, but that meant there was no disaster or explosion on the fringe and Boris behaved himself. And then Cameron topped it all.

The speech was authentically Conservative . Stripped of the usual drivel about the Coalition, it had a proper argument at its heart about the extension of opportunity. For someone deemed a good communicator, Cameron has often struggled to explain himself. Here he seemed to have found his voice, explaining properly why the themes of economic dynamism and social compassion are inextricably linked.

The quality and confidence of the attacks on Miliband should worry Labour a lot. They are, he claimed, the "party of one notion: borrowing".

Equally, one of the Labour leader's core assumptions is the idea that the government has its own money which it then gifts to taxpayers. This makes him a very hard sell when it comes to aspirational voters in the kinds of seats Labour must win to get a majority. So Cameron mined Margaret Thatcher in a powerful section which began: "This is how the tax system works, Ed". The Tories loved it, and good many voters will also find this theme attractive in the next few years if Cameron can keep making the case properly. If Labour can't get its head around this, then it needs to start familiarising itself with what happened when John Smith and Neil Kinnock did their stuff in 1992.